In 1992, 1,700 scientists issued the World Scientist’s Warning to Humanity. It asserted that we were on a path to ruining our natural world. 25 years later another group of more than 15,000 scientists have issued a second notice. Rick Pantaleo and his guests - Peter Frumhoff, Union of Concerned Scientists, Cambridge, Massachusetts and Erle Ellis, University of Maryland, Baltimore County - discuss various aspects of the report.